This invention relates to commercial refrigerator doors of the general type used to provide access to the interior of built-in refrigerator compartments of the kind used in grocery stores, for example, and more particularly to a refrigerator door structure constructed of fiberglass reinforced thermoplastics which may be individually constructed, packaged, shipped and installed.
Commercial refrigerator doors of this type generally comprise glass panels mounted in metal frames for use in connection with refrigerator display facilities which may be built-in in large grocery stores or super markets or may be self-contained refrigerator cabinets. Appropriate shelving is generally provided behind the glass panel refrigerator doors in which goods such as milk, cold drinks, perishable goods, or frozen foods, for example, may be displayed for sale. The customer selects the goods desired by looking through the glass panel of the door and removing the goods from the refrigerator. A closure means is generally provided biasing the door to its closed position in order to automatically close the door after it has been opened by the customer.
Since the refrigerated compartments on which the refrigerator doors are used are maintained below normal ambient temperature and often below a freezing temperature, the doors generally utilize a plurality of spaced panes of glass with dead air spaces therebetween in order to provide thermal insulation. The metal frames containing the glass panels may be provided with electrical heaters to prevent the condensation of moisture or the formation of frost on the frame and, in many cases, the glass may also be electrically heated.
A number of doors are generally provided in the opening of a refrigerated compartment in order to enable a customer to obtain access to a particular part of the refrigerated compartment where the desired goods are located. This minimizes the loss of cold air when access to the compartment is desired.
While these refrigerator doors have proven to be effective in carrying out their intended purposes, it is still desireable to provide a refrigerator door constructed of a lighter material such as fiberglass or fiberglass reinforced thermoplastics, so as to reduce opening efforts and transportation costs, while providing for easier manufacturing and assembly of a transparent refrigerator door.
While a wide variety of thermosetting reinforced plastics are available for utilization in the manufacture of such refrigerator doors, the tensile strength of these thermoplastics can be at least doubled by the addition of glass reinforcement. Further, unlike thermosetting reinforced plastics, fiberglass reinforced thermoplastic compounds may be used in conventional molding equipment to produce structural components having increased strength and rigidity, while exhibiting a marked decrease in the co-efficient of thermal expansion. Other beneficial effects achieved with the utilization of fiberglass reinforced thermoplastics are: retention of izod impact strength at very low temperatures, marked improvement in deflection temperatures, increases in hardness and abrasion resistance, as well as, decreases in mold shrinkage, creep, and dimensional changes with humidity.
It is therefore an object of this invention to provide a refrigerator door structure of lighter weight, and which has improved insulation characteristics as compared to conventional doors of the same dimension.
It is also an object of this invention to provide a refrigerator door structure which aids in the reduction of operating energy required by a refrigerator. It is still a further object of this invention to provide a lighter, transparent refrigerator door utilizing fiberglass or other lighter material for the frame and door to reduce opening effort and transportation problems.